1. Field of the Invention
The present invention relates to a photosensitive composition used in a manufacturing process of semiconductors, such as IC, manufactures of liquid crystals, circuit substrates of thermal heads and the like, and other photo-fabrication processes, and also relates to a composition used for the photosensitive composition and a pattern forming method using the photosensitive composition. More specifically, the invention relates to a photosensitive composition suitable in cases of using far ultraviolet rays of 250 nm or less, preferably 220 nm or less, as an exposure light source and electron beams as an irradiation source, and a pattern forming method using the same.
2. Description of the Related Art
Chemical amplification photosensitive compositions are pattern-forming materials capable of generating an acid at a part irradiated with radiation such as far ultraviolet ray, changing the solubility in a developing solution of the irradiated part and non-irradiated part with actinic radiation by the reaction with the acid as a catalyst, and forming a pattern on a substrate.
When a KrF excimer laser is used as an exposure light source, resins having poly(hydroxystyrene) as a fundamental skeleton that is small in absorption in the region of 248 nm are mainly used, so that high sensitivity and high resolution are secured and a good pattern is formed as compared with conventional naphthoquinonediazide/novolak resins.
On the other hand, when a light source of further shorter wavelength, e.g., an ArF excimer laser (193 nm), is used as an exposure light source, since compounds having an aromatic group substantially show large absorption in the region of 193 nm, even the above chemical amplification photosensitive compositions are not sufficient.
Therefore, resists for an ArF excimer laser containing a resin having an alicyclic hydrocarbon structure have been developed. As photo-acid generators capable of generating an acid at a part irradiated with radiation such as far ultraviolet ray, various compounds have been developed. For example, compositions containing a compound capable of generating a bis(sulfonyl)imidic acid upon irradiation with far ultraviolet rays are disclosed. (Refer to JP-A-2003-261529, JP-A-2003-231673, JP-A-2002-268223, JP-A-2004-12554, JP-A-2004-62154, and WO 2005/040,922).
However, these compounds are still insufficient in various points and further improvements are required. For example, it has come to be known that unevenness of in-plane temperature in a wafer in heating by a hot plate and the like after exposure (PEB: Post Exposure Bake) influences a pattern to be obtained, and when a wafer having a large aperture is used, line widths of a pattern obtained in the wafer are various. It is required to improve such PEB temperature dependency.
Further, it is difficult to reconcile the improvement of PEB temperature dependency with the widening of exposure latitude, so that it is desired to improve PEB temperature dependency and exposure latitude at the same time.